The present invention relates generally to low dielectric constant materials used for the intermetal dielectric layer and more particularly to the use of fluorine containing low dielectric constant materials for intermetal dielectric layers for technologies of 0.18 xcexcm and below.
The speed and reliability of semiconductor integrated circuits are coming to be more and more governed by the on-chip interconnects. Advanced chips employ multilevel on-chip interconnects usually comprising aluminum alloy lines, alluminum alloy or tungsten plugs for interlevel/intermetal contact/via holes, and fluorosilicate glass (fluorinated silicon dioxide, SiOxFy) as intermetal and interlevel dielectrics.
The speed performance of advanced chips, such as used for microprocessors and digital signal processors using sub-0.18 xcexcm complementary metal oxide semiconductor (CMOS) technologies and beyond is limited by the interconnect signal propagation delays. The signal propagation delay for advanced interconnects is limited by the parasitic resistive, capacitive, and inductive elements. These include the metal interconnect xe2x80x9cRCxe2x80x9d delays, capacitive noise or cross-talk, and inductive noise and cross-talk.
As chip dimensions are scaled down, the metal interconnect line widths and pitches are also scaled down accordingly. This means that the intermetal/interlevel dielectric layers (IMD and ILD layers) must be thinner. To reduce capacitive effects with the IMD/ILD materials, low dielectric constant (low-k) dielectric materials have been developed which have k values in the range of 3.2 down to 2.0. However, these low-k dielectrics complicate the backend of line (BEOL) process because of their inferior thermal stability as well as their electrical, mechanical, and thermal conductivity properties compared to conventionally used silicon oxide (SiOx).
High-density plasma (HDP) deposited fluorinated silica glass (FSG) intermetal dielectric (IMD) films have been of high interest for submicron devices due to its low dielectric constant (k) and good gap-filling capability. However HDP FSG has several problems from a process integration aspect, such as fluorine out-gassing, fluorine attack on conductors, etc. Fluorine out-gassing will cause voids in the vias which can lead to open vias. Fluorine attack on conductors during FSG deposition will clip away the corners of metal lines to leave metal lines having xe2x80x9cpearxe2x80x9d shaped cross-sections. Fluorine attack on conductors after FSG deposition due to the fluorine out-diffusion under thermal stress will lead to conductor fluoride in the metal line which will cause the critical dimension (CD) of the metal line to be lower than specified.
To prevent problems with HDP FSG, one attempt has been to use a very thick FSG film followed by a chemical-mechanical polishing (CMP) of the FSG to more than half its thickness and then capping with a silicon rich oxide (SRO) layer. This approach can reduce fluorine out-diffusion, but cannot totally eliminate it, and fluorine out-gassing into the vias and the xe2x80x9cpearxe2x80x9d shaped metal line problems still occur. At the same time, this method also creates some other problems like lithography CD control variation due to the impact from the SRO unmasking. The use of thick FSG films also leads to low throughput of the FSG process and high cost of ownership (COO). The FSG CMP integration is also a problem.
A solution to the above problems has been long sought, but has long eluded those skilled in the art.
The present invention provides an intermetal dielectric structure for integrated circuits having a premetal dielectric and a metal line thereon, with a halogen-barrier liner on the premetal dielectric layer and the metal lines, a halogen-containing dielectric layer over the halogen-barrier liner, a halogen-barrier film over the halogen-containing dielectric layer, and a non-halogen-containing dielectric layer over the halogen-barrier film. The structure is not subject to halogen attack on the metal lines while having a stable halogen containing dielectric layer with less halogen out-gassing and out-diffusion.
The present invention provides an intermetal dielectric structure for integrated circuits having a premetal dielectric and a metal line thereon, with a halogen-barrier liner on the premetal dielectric layer and the metal lines, a halogen-containing dielectric layer over the halogen-barrier liner, a halogen-barrier film over the halogen-containing dielectric layer, and a non-halogen-containing dielectric layer over the halogen-barrier film. Vias through the halogen-containing dielectric layer are treated to have non-halogen-containing regions around the vias. The structure is not subject to halogen attack on the metal lines or vias while having a stable halogen containing dielectric layer with less halogen out-gassing and out-diffusion.
The above and additional advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description when taken in conjunction with the accompanying drawings.